聚酯类生物降解塑料的降解行为

开发可完全生物降解的高分子材料是解决环境污染问题的一种有效途径。其中,脂肪族聚酯是公认的一类最有发展前景的可完全生物降解聚酯,由于可在自然环境中被降解成CO2和H2O而受到青睐。降解塑料在微生物作用下的降解行为受到外部环境和聚酯自身特性的影响。外部环境包括菌种、温度、湿度等;聚酯特性包括分子结构、分子量、熔点、结晶度等。从生物降解微生物、生物降解实验方法及生物降解机理三方面对PBS类降解塑料的降解行为进行论述。     

生物降解聚酯降解性能调控研究进展

综述了聚合物分子结构设计、聚合物共混改性以及复合材料配方设计等生物降解聚酯降解速率调控方法,分析了生物降解聚酯降解性能调控面临的问题并展望其前景,以期为制备具有高性能、时控性和完全降解性的生物降解聚合物材料提供理论基础。     

聚酯链结构定制及其构效关系

聚酯材料的物理性能与可生物降解性为其聚集态结构所决定,而聚合物链的化学组成、序列和拓扑结构又是决定聚合物聚集态结构的最关键因素。为此,本文从基于聚合过程调控的聚酯链结构定制出发,总结了嵌段、长支链、梳状、星型、超支化与树枝状结构聚酯的定制方法;评述了链结构与聚酯热与力学性能之间的构效关系,探讨了链结构对聚酯降解性能的影响规律,前人的研究表明共聚物嵌段长短影响着结晶聚集态结构,长支链的存在有助于聚酯结晶温度与结晶度的提高;链的结晶能力、链长及亲疏水性决定了聚酯的降解性能。文中还对高性能可生物降解聚酯材料的开发进行了展望。     

以反丁烯二酸合成的不饱和脂肪族聚酯的生物降解性研究

以反丁烯二酸、一缩二乙二醇和1,4-丁二醇为原料,采用熔融缩聚法合成了不饱和脂肪族聚酯和共聚酯,在37℃下,用含有脂肪酶的磷酸缓冲溶液对聚酯的生物降解性进行了研究,讨论了聚酯结构、组成及C=C双键的交联度对生物降解性的影响。结果表明,对于粘稠液体状的聚酯,C=C双键的引入,没有明显的改变其生物降解性;对于固体状的聚酯,C=C双键引入后,熔点(Tm)和结晶度增加;聚酯部分降解后,其热力学性能(Tm、-ΔHm)和结晶度都升高;对于交联后的聚酯,交联度越高,生物降解性越差。     

聚丙交酯及可降解脂肪族聚酯类纤维的结构与生物降解性能

以聚丙交酯为代表讨论了可生物降解聚酯类纤维的结构特征与生物降解性能,对聚酯类纤维生物降解的机理、影响因素进行分析,指出聚合物的分子质量及分子链结构、聚集态结构、环境的温度、湿度、pH值及酶种类等因素对其降解性能有明显的影响,合理控制这些因素,可对其降解速度实现人为控制,以适应不同用途的需要.     

生物降解聚酯及其应用

介绍了生物降解聚酯及其应用现状,分析了生物降解的速度控制,指出了开发生物降解材料的必要性以及用生物资源为原料制造生物降解材料是21世纪的发展方向。     

产品开发

生物降解材料新秀——共聚酯前途光明 目前已开发成功的生物降解材料聚乳酸、聚羟基烷酸酯、聚已内酯、聚碳酸亚丙酯、聚碳酸亚乙酯、聚丁二醇丁二酸酯、聚乙烯醇等,由于产品性能和成本等因素,在大范围推广受限,而脂肪-芳香族共聚聚酯作为生物降解材料新秀,兼具脂肪族聚酯良好的生物降解性、生物相容性和芳香族聚酯优异的力学性能及热稳定性,而且生产成本低,开发和市场前景非常广阔。     

聚烯烃降解母料

美国 Willow Ridge Plastics公司和 ECMBiofilms公司宣称已开发出可使聚乙烯 ( PE)和聚丙烯 ( PP)产品像纸张和木材一样降解的有效方法 ,就是在聚烯烃 ( PO)载体中加入专用添加剂母料即可使聚烯烃产品 5年内完全生物降解 ,其制品成本价格与普通 LDPE和 PP相当。　　与原有可生物降解聚合物相对比 ,他们的方法具有价格优势。按每立方英寸的平均价格来计算 ,可生物降解型共聚聚酯和乳酸聚合物至少比聚烯烃添加剂母料贵 1 0倍。　　 ECM公司总裁 Robert声称 ,这是唯一可使大批量薄膜、片材、注射制品等降解的有效可行方法。ECM公司…     

用可再生资源制备的生物降解聚酯

本文叙述了由１，４∶３，６－双失水己糖醇的３种立体异构体［１，４∶３，６－双失水－Ｄ－葡糖醇（１）、１，４∶３，６－双失水－Ｄ－甘露糖醇（２）和１，４∶３，６－双失水－Ｌ－艾杜糖醇（３）］分别与琥珀酰氯（４ａ）、戊二酰氯（４ｂ）、己二酰二氯（４ｃ）和癸二酰氯（４ｄ）进行本体聚合而合成一系列聚酯的过程，并对这些聚酯的生物降解能力进行了探讨。用３种不同的方法（即活化污泥降解、土壤埋藏降解和酶催化降解）研究了这些聚酯的生物降解能力，其中只有由３号反应物制备的聚酯（７ｂ～７ｄ）和由２与４ａ制备的聚酯６ａ，因其为晶态聚合物而几乎不可生物降解，生成的其他非晶态聚酯或多或少可发生生物降解，这些聚酯的生物降解能力因其分子结构的不同而差异很大。将这些聚酯放在经过抗生素处理的土壤中进行土埋降解，同时用电子扫描显微镜观察，发现由１分别４ｂ和４ｃ制备的聚酯５ｂ和５ｃ可被细菌和丝状真菌所降解，而由１与４ｄ制备的聚聚酯５ｄ主要被丝状真菌所降解。     

可生物降解聚酯

中国石化上海石油化工股份有限公司采用独创工艺研制成功可降解聚酯,并完成了中试。这种新型生物塑料耐热性有了很大提高,热变形温度超过100℃,可以满足通用塑料使用要求。该聚酯用品废弃后,可被土壤中微生物分解。可生物降解聚酯经过94天降解,降解达到62．1％,符合国际标准。     

Biodegradable polymers and environmental interaction

Biodegradable polymers are by definition those that degrade as a result of the action of microorganisms and/or enzymes. The rate of this biodegradation may vary from hours to years depending on the molecular architecture of the polymer in question. Biopolymers like lignin take years to degrade while many proteins and polysaccharides degrade within hours to days. The same is true for the synthetic biodegradable polymers where polyethylene is sometimes regarded as inert to biodegradation while polyanhydrides are rapidly biodegradable. The influence of structure, morphology, and surface area on the biodegradability are discussed, with polyesters and degradable polyethylene (with pro-oxidant and/or biodegradable additives) as examples. The rate of biodegradation is controllable by choosing the appropriate molecular architecture. In addition to this the environmental interaction of these polymers should be determined. The degradation product pattern of biodegradable polymers should be compatible with the natural degradation mechanisms (i.e., catabolisms).     

A review of biodegradable polymers: uses,current developments in the synthesis and characterization of biodegradable polyesters,blends of biodegradable polymers and recent advances in biodegradation studies

This review considers the uses of biodegradable polymers in terms of their relevance within current plastic waste management of packaging materials, biomedical applications and other uses; research papers and patents are catalogued. The chemical synthesis of polyesters and the microbial production of poly(hydroxyalkanoate)s, including recent publications in these areas, are covered and methods of characterization and structural analysis are outlined. Current research into two- and three-component blends is reviewed as a method of reducing overall costs and modifying both properties and biodegradation rates of materials. Finally, there is a summary of degradation processes. Both abiotic and biotic reactions are discussed, together with the development of biodegradation test methods, particularly with respect to composting. © 1998 Society of Chemical Industry     

Structural Insights into Carboxylic Polyester-Degrading Enzymes and Their Functional Depolymerizing Neighbors

Esters are organic compounds widely represented in cellular structures and metabolism, originated by the condensation of organic acids and alcohols. Esterification reactions are also used by chemical industries for the production of synthetic plastic polymers. Polyester plastics are an increasing source of environmental pollution due to their intrinsic stability and limited recycling efforts. Bioremediation of polyesters based on the use of specific microbial enzymes is an interesting alternative to the current methods for the valorization of used plastics. Microbial esterases are promising catalysts for the biodegradation of polyesters that can be engineered to improve their biochemical properties. In this work, we analyzed the structure-activity relationships in microbial esterases, with special focus on the recently described plastic-degrading enzymes isolated from marine microorganisms and their structural homologs. Our analysis, based on structure-alignment, molecular docking, coevolution of amino acids and surface electrostatics determined the specific characteristics of some polyester hydrolases that could be related with their efficiency in the degradation of aromatic polyesters, such as phthalates.     

Biodegradability assessment of aliphatic polyesters‐based blends using standard methods

Important information concerning polymer's final fate in the environment can be achieved in biodegradation studies. In this context, the focus of this study was to evaluate the biodegradability of blends containing aliphatic polyesters using standard methods. Blends of high‐density polyethylene, biodegradable polymer, and polyethylene modified with maleic anhydride (used as compatibilizer) were prepared in a corotating twin‐screw extruder. Biodegradable polymers used were poly(lactic acid) (PLA), poly(ε‐caprolactone) (PCL), and Mater‐Bi (thermoplastic starch with PLA or PCL). Biodegradation tests were carried out using two standard methods: (i) ISO 14851 (1999), biochemical oxygen demand in a closed respirometer and (ii) ASTM G 22‐76, microbial growth of test microorganisms. Both biodegradability tests suggested that the blend containing PCL is more biodegradable than the one containing PLA. Addition of starch increased the biodegradability of the PLA blend. The biodegradability of the blends evaluated in this study by the biochemical oxygen demand method ranged from 22% (PLA 60) to 52% for corn starch/PCL 30/70 (% wt) (SPCL 70). Therefore, the blends may not be considered “readily biodegradable” according to the OECD standard. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Biodegradability of polyesters having tetrahydropyran rings in their backbones

Biodegradability of several homo- and copolyesters, containing tetrahydropyran rings in their backbones with or without pendant groups, was investigated by degradation tests, both in soil and in an activated sludge. These polyesters were hydrolytically degraded to lower molecular weight compounds, and eventually to hydroxytetrahydropyran carboxylic acids, at different rates, depending on their molecular structure. Quantitative determination of carbon dioxide, generated during the treatment with the activated sludge, showed that the hydrolysates from polyesters 2 and 10 , without pendant alkoxycarbonyl groups, were catabolized by microorganisms. It was concluded from these results that at least the polyesters without pendant groups were biodegradable, and that polyester 10 , consisting of 2,6-linked tetrahydropyran rings, underwent biodegradation more readily than polyester 2 , consisting of 2,5-linked tetrahydropyran rings. © 1994 John Wiley & Sons, Inc.     

Biodegradability of Plastics

Plastic is a broad name given to different polymers with high molecular weight, which can be degraded by various processes. However, considering their abundance in the environment and their specificity in attacking plastics, biodegradation of plastics by microorganisms and enzymes seems to be the most effective process. When plastics are used as substrates for microorganisms, evaluation of their biodegradability should not only be based on their chemical structure, but also on their physical properties (melting point, glass transition temperature, crystallinity, storage modulus etc.). In this review, microbial and enzymatic biodegradation of plastics and some factors that affect their biodegradability are discussed.     

Biodegradability of Novel Polylactide and Polycaprolactone Materials with Bacteriostatic Properties Due to Embedded Birch Tar in Different Environments

The microbial biodegradation of new PLA and PCL materials containing birch tar (1–10% v/v) was investigated. Product of dry distillation of birch bark (Betula pendula Roth) was added to polymeric materials to obtain films with antimicrobial properties. The subject of the study was the course of enzymatic degradation of a biodegradable polymer with antibacterial properties. The results show that the type of the material, tar concentration, and the environment influenced the hydrolytic activity of potential biofilm degraders. In the presence of PCL films, the enzyme activities were higher (except for α-D-glucosidase) compared to PLA films. The highest concentration of birch tar (10% v/v) decreased the activity of hydrolases produced by microorganisms to the most significant extent; however, SEM analysis showed the presence of a biofilm even on plastics with the highest tar content. Based on the results of the biological oxygen demand (BOD), the new materials can be classified as biodegradable but, the biodegradation process was less efficient when compared to plastics without the addition of birch tar.     

天然纤维素基生物降解塑料研究进展

综述了纤维素基生物降解塑料共混法、化学改性法及微生物法三种典型制备方法,介绍了C02释放量检测、生物降解半衰期检测、生物降解塑料分子量检测、微生物侵蚀形貌观察及生物降解性能指标检测等生物降解性评价机制。纤维素基生物降解塑料是未来新材料发展的重要领域,将会朝着低成本、广应用、降解速度可控和完全降解的方向发展。     

PBS基聚酯合成工艺的研究进展

PBS(聚丁二酸丁二醇酯)是种具有良好生物降解性的聚酯塑料,对PBS基聚酯的合成进行了总结和比较,介绍了PBS基聚酯合成的研究进展。指出进一步优化合成工艺来合成高分子量的PBS基聚酯仍然是一项挑战性的工作。     

Branched aliphatic polyesters by ring-opening (co)polymerization

The rapid development of biodegradable and biocompatible materials for biomedical applications is reflected in the search for new methods for aliphatic polyester modification applicable in this field. One possible approach is modification by changes to the polymer topology.This review covers the main methods of synthesis of branched aliphatic biodegradable and biocompatible (co)polyesters, where the ring-opening polymerization (ROP) of cyclic esters or cyclic carbonates is the leading process. First, literature examples of ring-opening multibranching polymerization (ROMBP) of AB₂-type hydroxyl-substituted cyclic lactones, lactides and carbonates are cited followed by the presentation of the application of AB-type cyclic esters and additionally AB₂ cyclic ethers or esters as “branching monomers” for the synthesis of branched polyesters based on polycaprolactone (PCL), polylactide (PLA) and polyglycolide (PGA). In the following part, methods involving the combination of the ROP of AB-type cyclic esters and condensation processes leading to branched structures are summarized. Other related strategies leading to “dendri-star” or “core–shell” copolyesters are also discussed. Several examples of approaches to PCL and PLA graft copolymer syntheses are also shown. The advantages and disadvantages of the presented methodologies of branched polyester synthesis are highlighted. Finally, the influence of the branched structure on the properties of the presented class of polyesters, important from the application point of view, is considered.